Vertical alignment method of vertical type micro LED and LED assembly manufacturing method using the same

ABSTRACT

Disclosed is a vertical alignment method of a micro light emitting diode (LED), which is capable of vertically aligning vertical type micro LEDs each having a nano size or micro size and stably maintaining an aligned state on a structural basis. The method includes preparing a substrate provided with a plurality of through holes formed in a thickness direction, locating micro LEDs to be aligned on the substrate in a state of being included in a suspension which provides buoyancy, and generating a pressure difference between an upper side and a lower side of the substrate and moving the suspension in a downward direction through the through holes of the substrate to induce the micro LEDs included in the suspension to be aligned in an upright state by being at least partially inserted into the through holes.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No. 10-2019-0121483 (filed on Oct. 1, 2019), which is incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to a vertical alignment method of a micro light emitting diode (LED), and more particularly, to a vertical alignment method of a micro LED capable of vertically aligning vertical type micro LEDs each having a nano size or micro size and stably maintaining an aligned state on a structural basis and an LED assembly manufacturing method using the same.

Generally, a light emitting diode (LED) is a well-known semiconductor light emitting element which converts current to light, and accordingly, is called the revolution of light as a green material which consumes very little energy, has a semi-permanent lifespan, and is eco-friendly due to high light conversion efficiency, and has been widely used as a light source for image display of electronic devices such as information and communication devices.

Recently, due to the development of compound semiconductor technology, high-brightness red, orange, green, blue and white LEDs have been developed, and thus applied to many fields such as traffic lights, mobile phones, automobile headlights, outdoor billboards, a liquid crystal display (LCD) back light unit (BLU), and indoor and outdoor lighting, and an active study is being performed at home and abroad. Specifically, a GaN-based compound semiconductor having a wide bandgap is a material used to manufacture an LED semiconductor which emits light of the green, blue and ultraviolet light regions, and since white LED elements can be manufactured using blue LED elements, many studies are being performed.

Among the above-described studies, a study for applying a micro LED element or the like manufactured in a nano or micro unit to lighting, displays, and the like is continuing. In this study, areas which are continuously attracting attention are electrodes capable of applying power to the micro LED element, a purpose of use, an alignment method for reducing a space occupied by the electrodes, electrode alignment, and a method of mounting a micro LED on the aligned electrodes.

The micro LED has a difficulty that it is very difficult to align freely as desired due to a size constraint. The micro LED is nano-scaled or micro-scaled, and thus cannot be manually arranged and mounted on an electrode area. However, despite the above limitations, as shown in FIG. 1, a technique of a method of laying down and aligning LEDs 30 each having a first conductive layer 31, a second conductive layer 32, and an active layer 33 on a substrate 10, on which electrodes 20 a and 20 b are formed, in a horizontal direction is disclosed.

However, when the LEDs 30 are aligned in the horizontal direction, since a light output direction faces toward a side surface rather than a front surface or back surface, and thus light efficiency and a light quantity are lowered, and as an area occupied by one laid LED 30 is increased, the degree of integration is reduced, and the LEDs 30 are difficult to be applied to a high resolution display. Further, since the first conductive layer 31 and the second conductive layer 32 of the LED 30 are mixed with the first conductive layer 31 and the second conductive layer 32 of the LED 30 disposed in a different column, it is difficult to connect the electrodes 20 a and 20 b.

Further, since the LEDs 30 are self-aligned with respect to the substrates 10 and the electrodes 20 a and 20 b without a structural basis by a force such as a dielectrophoretic force, accurate alignment is not achieved and an aligned state is also difficult to be stably kept.

(Patent Document 1) Korean Laid-open Patent No. 2016-0059576 (May 27, 2016)

SUMMARY

The present disclosure is directed to providing a vertical alignment method of a vertical type micro light emitting diode (LED) capable of vertically aligning vertical type micro LEDs each having a nano size or micro size and stably maintaining an aligned state on a structural basis and an LED assembly manufacturing method using the same.

According to an aspect of the present disclosure, there is provided a vertical alignment method of a micro LED which aligns a micro LED whose vertical width is greater than a lateral width, the vertical alignment method including: preparing a substrate provided with a plurality of through holes formed in a thickness direction; locating micro LEDs to be aligned on the substrate in a state of being included in a suspension which provides buoyancy; and generating a pressure difference between an upper side and a lower side of the substrate and moving the suspension in a downward direction through the through holes of the substrate to induce the micro LEDs included in the suspension to be aligned in an upright state by being at least partially inserted into the through holes.

Here, the suspension including the micro LEDs may be applied on an upper surface of the substrate and thus the micro LEDs may be located on the substrate and one through hole of the substrate may correspond to one micro LED.

Further, each of the micro LEDs may be provided so that a lower portion has a high density in comparison with an upper portion, and thus the lower portions of the LEDs having a relatively high density may be guided to move in a downward direction in the suspension moving downward when the micro LEDs are aligned.

The micro LED may be formed to have a diameter which is uniform from a lower end portion to an upper end portion.

The micro LED may be formed to have a diameter which gradually increases from an upper end portion to a lower end portion.

The micro LED may be formed to have a diameter which gradually increases from a lower end portion to an upper end portion.

The micro LED may be fixed by crossing an upper inlet of the through hole of the substrate.

The substrate may be provided so that each of the through holes has the same inner diameter from an upper side to a lower side thereof.

The substrate may be provided so that each of the through holes has an inclined portion in which an inner diameter is changed from an upper side to a lower side thereof.

The substrate may be provided so that each of the through holes has an inclined portion in which an inner diameter gradually decreases from an upper side to a lower side thereof, and thus the micro LED may be fixed by crossing at one point of the inclined portion in a state of being inserted into the through hole of the substrate.

The substrate may be provided with various types of through holes having inner diameters of different sizes, the micro LEDs may be provided in various types having diameters of sizes corresponding to the various types of through holes, and the LEDs may be classified from large to small in size to be sequentially inserted into the through holes.

Three types of through holes having inner diameters of different sizes may form one group in the substrate, and an R LED for red light emission, a G LED for green light emission, and a B LED for blue light emission may be inserted into the three types of through holes forming the one group.

A stopper plate having discharge holes may be installed on the lower surface of the substrate to allow only the suspension to pass downward through the discharge holes and block the micro LEDs so that the micro LEDs remain in the through holes of the substrate.

A first conductive layer, an active layer, a second conductive layer may be sequentially located from a lower layer to an upper layer in the micro LED, one of the first conductive layer and the second conductive layer may be an n-type nitride semiconductor layer, and the other of the first conductive layer and the second conductive layer may be a p-type nitride semiconductor layer.

The micro LED may have a vertical width of 100 nm to 10 μm.

Meanwhile, an LED assembly manufacturing method according to the present disclosure may have a technical feature that the micro LEDs are vertically aligned by the vertical alignment method of the micro LED, and a first electrode and a second electrode connected to the first conductive layer and the second conductive layer of the micro LED are respectively deposited on the lower surface and an upper surface of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present disclosure will become more apparent to those of ordinary skill in the art by describing exemplary embodiments thereof in detail with reference to the accompanying drawings, in which:

FIG. 1 is a reference diagram for describing a light emitting diode (LED) assembly according to the related art;

FIG. 2 is a flow chart of an LED assembly manufacturing method according to an embodiment of the present disclosure;

FIG. 3 is a perspective view of vertical type micro LEDs to be aligned in the LED assembly manufacturing method according to the embodiment of the present disclosure;

FIG. 4 is a configuration view for describing an aligning device which is used to align the micro LEDs when an LED assembly according to the embodiment of the present disclosure is manufactured;

FIGS. 5A to 5D are a series of reference diagrams for describing the LED assembly manufacturing method according to the embodiment of the present disclosure;

FIG. 6 is a cross-sectional view of the LED assembly manufactured through the LED assembly manufacturing method according to the embodiment of the present disclosure;

FIGS. 7A and 7B are a series of reference diagrams for describing an LED assembly manufacturing method according to a first modified embodiment of the present disclosure;

FIGS. 8A to 8C are a series of reference diagrams for describing an LED assembly manufacturing method according to a second modified embodiment of the present disclosure;

FIG. 9 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a third modified embodiment of the present disclosure;

FIG. 10 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a fourth modified embodiment of the present disclosure;

FIG. 11 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a fifth modified embodiment of the present disclosure;

FIG. 12 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a sixth modified embodiment of the present disclosure; and

FIGS. 13 to 16 are reference diagrams for describing that a first electrode may be formed before the micro LEDs are aligned in the LED assembly manufacturing method according to the embodiment of the present disclosure.

DETAILED DESCRIPTION

A light emitting diode (LED) assembly manufacturing method using a vertical alignment method of micro LEDs according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Since the present disclosure may be variously changed and have various embodiments, particular embodiments will be exemplified and described in the drawings. However, the present disclosure is not limited to the particular embodiments and includes all changes, equivalents, and substitutes within the spirit and the scope of the present disclosure. In the description of the drawings, similar reference numerals are used for similar elements. In the accompanying drawings, sizes of structures are shown to be enlarged in comparison with actual sizes for clarity of the present disclosure, or downscaled in comparison with the actual sizes to understand schematic configurations.

It should be understood that, although the terms “second,” “first,” and the like may be used herein to describe various elements, the elements should not be limited by the terms. The terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element without departing from the scope of the present disclosure. Meanwhile, unless otherwise defined, all terms including technical or scientific terms used in the present disclosure have meanings which are the same as those of terms generally understood by those skilled in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Embodiment

Hereinafter, the LED assembly manufacturing method according to the embodiment of the present disclosure will be described.

FIG. 2 is a flow chart of the LED assembly manufacturing method according to the embodiment of the present disclosure, FIG. 3 is a perspective view of vertical type micro LEDs to be aligned in the LED assembly manufacturing method according to the embodiment of the present disclosure, FIG. 4 is a configuration view for describing an aligning device which is used to align the micro LEDs when an LED assembly according to the embodiment of the present disclosure is manufactured, and FIGS. 5A to 5D are a series of reference diagrams for describing the LED assembly manufacturing method according to the embodiment of the present disclosure. As described above, the LED assembly manufacturing method according to the embodiment of the present disclosure includes an operation of preparing a substrate (S110), an operation of applying a suspension (S120), an operation of aligning the micro LEDs (S130), and an operation of forming electrodes (S140).

In the operation of preparing the substrate (S110), a substrate 120 provided with a plurality of through holes 121 formed in a thickness direction is prepared. The substrate 120 is provided to have a thickness greater than a vertical width of each of micro LEDs 110, and the through holes 121 formed in the substrate 120 serve to fix the micro LEDs 110 in at least a partially inserted state. In order to prepare the through holes 121 in the substrate 120, one of various known methods including a super drill, laser drilling, etching may be selected and used according to the size of a diameter. An inner diameter of the through hole 121 of the substrate 120 is determined according to a lateral width of the micro LED 110, and since the lateral width of the micro LED 110 is 100 nm to 5 μm, the diameter of the through hole 121 may be formed to be 100 nm to 5 μm. The through hole 121 of the substrate 120 may be formed to correspond to the shape and size of the micro LED 110 to support and fix the micro LED 110 in an inserted state, and as shown in FIG. 5D, the substrate 120 according to the embodiment of the present disclosure has a thickness greater than the vertical width of the micro LED 110 to stably support the micro LEDs 110 in a state in which the micro LEDs 110 are completely inserted. However, the thickness of the substrate 120 may be modified to be smaller than or equal to the vertical width of the micro LED 110, and descriptions thereof will be described later in detail.

Here, the substrate 120 may be provided as a substrate formed of a transparent material such as sapphire (Al₂O₃) and glass, and may be selected from a material group including GaN, SiC, ZnO, Si, GaP, GaAs, and the like.

In the operation of applying the suspension (S120), as shown in FIG. 5A, since a suspension 140 including the micro LEDs 110 to be aligned is applied on an upper surface of the substrate 120, the micro LEDs 110 are located on the substrate 120. Here, applying the suspension 140 may refer to locating the suspension 140 in a state of being brought into contact with a surface of the substrate 120, and the suspension 140 used in this case may be used without limitation to any one type when not causing a corrosion problem of the micro LEDs 110 and the substrate 120 and providing buoyancy and dispersibility to the micro LEDs 110 at an appropriate level.

As shown in FIG. 3, the micro LED 110 included in the suspension 140 may be formed in a vertical type in which the vertical width is greater than the lateral width, wherein the vertical width is 100 nm to 10 μm, and the lateral width is 100 nm to 5 μm, but is not limited thereto. The micro LED 110 may be provided such that a first conductive layer 111, an active layer 112, and a second conductive layer 113 are sequentially formed from a lower layer to an upper layer, wherein the first conductive layer 111 is preferably formed of n-GaN which is an n-type nitride semiconductor layer, the active layer 112 is preferably formed of multi quantum wells (MQWs), and the second conductive layer 113 is preferably formed of p-GaN which is a p-type nitride semiconductor layer.

Further, the first conductive layer 111 may be one or more selected from semiconductor materials having a composition formula of InxAlyGa1-x-yN (0≤x≤1, 0≤y≤1, 0≤x+y≤1), for example, InAlGaN, GaN, AlGaN, InGaN, AlN, InN, and the like, and may be doped with a first conductive dopant (for example, Si, Ge, Sn, or the like). The first conductive layer 111 may have a thickness of 1.5 to 5 μm but is not limited thereto. The second conductive layer 113 may be one or more selected from semiconductor materials having a composition formula of InxAlyGa1-x-yN (0≤x≤1, 0≤y≤1, 0≤x+y≤1), for example, InAlGaN, GaN, AlGaN, InGaN, AlN, InN, and the like, and may be doped with a second conductive dopant (for example, Mg). The second conductive layer 113 may have a thickness of 0.08 to 0.25 μm but is not limited thereto.

Meanwhile, the active layer 112 may be used without limitation in a case of an active layer 112 included in general micro LEDs 110 used for lighting, displays, and the like. A cladding layer doped with a conductive dopant may be formed on at least one of an upper side and a lower side of the active layer 112, and the cladding layer doped with the conductive dopant may be implemented as an AlGaN layer or InAlGaN layer. In addition, materials such as AlGaN, AlInGaN, and the like may also be used for the active layer 112. In the active layer 112, when an electric field is applied, light is generated by a combination of electron-hole pairs. A thickness of the active layer 112 may be 0.05 to 0.25 μm but is not limited thereto. The first conductive layer 111, the active layer 112, and the second conductive layer 113 described above may be included as minimum configuration elements in a light emitting structure, and at least one of different phosphor layers adjacent to each layer, the active layer 112, and a semiconductor layer may be further included.

However, the micro LED 110 is not limited to any one, and may be used by selecting micro LEDs which meet the latest technology trends.

In the operation of aligning the micro LEDs (S130), as shown in FIG. 5B, a pressure difference between an upper side and a lower side of the substrate 120 is generated to move the suspension 140 in a downward direction through the through holes 121 of the substrate 120 in a state in which the suspension 140 including the micro LEDs 110 is applied on the upper surface of the substrate 120. That is, when a pressure P1 at the upper side of the substrate 120 is formed to be greater than a pressure P2 at the lower side of the substrate 120, since the suspension 140 located at the upper side of the substrate 120 tends to move to the lower side of the substrate 120 through the through holes 121, the suspension 140 passes through the through holes, and the micro LEDs 110 included in the suspension 140 are inserted into the through holes 121 while moving with the suspension 140.

To this end, as shown in FIG. 4, an aligning device 150 capable of imparting the pressure difference between the upper side and the lower side of the substrate 120 is needed. All devices which may form a pressure difference between the upper side and the lower side of the substrate 120 and may be precisely controlled such as a pressure pad connected to a vacuum pump and having a chamber 151 to be capable of suctioning the suspension 140 from the lower side of the substrate 120 through the through holes 121 may be used as the aligning device 150.

In this case, as shown in FIG. 4, a stopper plate 122 having discharge holes 122 a may be previously installed on a lower surface of the substrate 120 to allow only the suspension 140 to pass downward through the discharge holes 122 a and block the micro LEDs 110 so that the micro LEDs 110 remain in the through holes 121 of the substrate 120. Alternatively, engaging protrusions which slightly protrude may be formed to serve as stoppers at lower end portions or inner circumferential surfaces, which are adjacent to the lower end portions, of the through hole 121, and in the latter case, it may be difficult to form the engaging protrusions in the fine through holes 121. As described above, in order to ensure that the micro LEDs 110 moving through the through holes 121 of the substrate 120 together with the suspension 140 do not completely pass through the through holes 121 but are stopped and fixed in the middle, an additional member such as the stopper plate 122 may be used, and various methods such as modifying the micro LEDs 110 or the through holes 121, and the like may be used. Some configurations will be described later.

In the operation of aligning the micro LEDs (S130), it is important that the micro LEDs 110 should have correct directivity while moving in the downward direction with the suspension 140 to be inserted into the through holes 121 of the substrate 120, and to this end, each of the micro LEDs 110 is configured to have a greater density in a lower portion in comparison with an upper portion. That is, since a lower weight of the micro LED 110 per unit area is greater than an upper weight of the micro LED 110 per unit area, in a stationary state of the suspension 140 as shown in FIG. 5A, the micro LED 110 does not show directivity in a dispersed state, but in a state in which the micro LED 110 moves in the downward direction along the suspension 140 as shown in FIG. 5B, the micro LED 110 moves in a state in which the lower portion having a greater density than other portions faces the downward direction. Since a density difference between the lower portion and the upper portion of the micro LED 110, the size of the micro LED, and the density and viscosity of the suspension 140 mainly influence how quickly or accurately the micro LED 110 is oriented with movement of the suspension 140, these specifications may be precisely adjusted.

Some aspects according to the operation of aligning the micro LEDs (S130) are described, but the most important point is realizing a unique idea for moving the suspension 140 including the micro LEDs 110 through the through holes 121 of the substrate 120 so that a plurality of micro LEDs 110 are located in the through holes 121. In addition, a point that the plurality of micro LEDs 110 are simultaneously moved in one to one correspondence to a plurality of through holes 121 to be inserted into the through holes 121 with the correct directivity to be vertically aligned, and it is structurally possible to stably maintain the aligned state may be noted. Accordingly, stability may be significantly improved in comparison with a case in which the micro LEDs 110 are self-aligned by an electric field between two electrodes in a conventional horizontal alignment method. As described above, the alignment method of vertical type micro LEDs is performed in the operation of aligning the micro LEDs (S130), and in addition, the LED assembly may be manufactured when the following process for applying power to the micro LEDs 110 proceeds.

In the operation of forming the electrodes (S140), as shown in FIG. 5D, a first electrode 130 a and a second electrode 130 b are respectively deposited on the lower surface and the upper surface of the substrate 120, and are connected to the first conductive layers 111 and the second conductive layers 113 of the aligned micro LEDs 110 inserted into the through holes 121 of the substrate 120. Accordingly, when the power is applied to the electrodes, the micro LEDs 110 become capable of emitting light. In the operation of forming the electrodes (S140), since the plurality of micro LEDs 110 are aligned in the through holes 121 of the substrate 120 with the correct directivity through the former operations, a point that the first electrode 130 a and the second electrode 130 b may be easily connected to the first conductive layers 111 and the second conductive layers 113 of the micro LEDs 110 by only respectively depositing the first electrode 130 a and the second electrode 130 b on the lower surface and the upper surface of the substrate 120 may be noted.

Meanwhile, FIGS. 13 to 16 show that the electrodes may also be formed before the micro LEDs 110 are aligned. Specifically, as shown in the drawings, when each of the through holes 121 of the substrate 120 is formed in an inclined hole shape which becomes gradually broader from the lower side to the upper side (a modified shape will be described later), it does not require a separate stopper member such as the stopper plate 122 when the micro LEDs 110 are aligned and assists simplification of the overall process.

Through the operation of forming the electrodes (S140), it is possible to obtain the LED assembly in which the electrodes are formed in a state in which the LEDs 110 are stably and vertically arranged as shown in FIG. 5D.

FIG. 6 is a cross-sectional view of the LED assembly manufactured through the LED assembly manufacturing method according to the embodiment of the present disclosure.

As shown in the drawing, the LED assembly manufactured through the LED assembly manufacturing method according to the embodiment of the present disclosure includes a substrate 120 provided with a plurality of through holes 121 formed in a thickness direction, micro LEDs 110 standing and aligned in a state of being inserted into the through holes 121, and a first electrode 130 a and a second electrode 130 b respectively deposited on a lower surface and an upper surface of the substrate 120 to be connected to the micro LEDs 110.

The first electrode 130 a is deposited on the lower surface of the substrate 120 to be physically and electrically connected to a first conductive layer 111 of the micro LED 110, and the second electrode 130 b is deposited on the upper surface of the substrate 120 to be physically and electrically connected to a second conductive layer 113 of the micro LED 110.

The LED assembly is a device in which the micro LEDs 110 may be vertically aligned and stably maintain the aligned state by a completely new structure in which the micro LEDs 110 are inserted into and fixed to the through holes 121 of the substrate 120 formed in the thickness direction. Accordingly, unlike a conventional horizontal alignment method, since a problem that a first conductive layer and a second conductive layer are mixed and thus electrodes are difficult to be connected is solved and a light emitting direction is formed to be the same as a vertical direction in which the micro LEDs 110 are aligned, light efficiency and light quantity may be improved. In addition, various advantages such as a case in which the degree of integration of the micro LEDs 110 per the same area is significantly improved in comparison with the conventional horizontal alignment method and thus the micro LEDs 110 become very advantageous for application to high resolution displays, and the like may be expected.

The LED assembly manufacturing method according to the embodiment of the present disclosure is a method of changing a thickness of the substrate 120 (alternatively, a length of the through hole 121) on the basis of a vertical width of the micro LED 110, or changing a shape of each of the micro LED 110 and the through hole, and various modified embodiments are possible. This will be described below.

First Modified Embodiment

FIGS. 7A and 7B are a series of reference diagrams for describing an LED assembly manufacturing method according to a first modified embodiment of the present disclosure.

As described above, in the first modified embodiment of the present disclosure, in comparison with before modification, a through hole 121 of a substrate 120 is formed to have an inclined portion in which an inner diameter is not identically formed from an upper side to a lower side and gradually decreases from the upper side to the lower side, and a micro LED 110 is provided in a shape having a diameter which gradually increases from an upper end portion to a lower end portion. In the case of the micro LED 110 formed with a lower portion having a greater width than an upper portion like the above, since the lower portion of the micro LED 110 having the greater width tends to naturally move in a downward direction when moving in the downward direction along a suspension 140, it is relatively advantageous for the micro LED 110 to be correctly upright and aligned.

According to the configurations of the first modified embodiment, as shown in FIG. 7B, there is an advantage in that the lower end portion of the micro LED 110 is fixed by crossing the inclined portion of the through hole 121 of the substrate 120 even when a separate stopper member is not provided.

Second Modified Embodiment

FIGS. 8A to 8C are a series of reference diagrams for describing an LED assembly manufacturing method according to a second modified embodiment of the present disclosure.

As shown in the drawings, the second modified embodiment of the present disclosure is a method which is advanced one step further from the first modified embodiment, wherein a substrate 120 having a plurality of types of through holes having different inner diameters is provided, and micro LEDs are provided in a plurality of types having diameters corresponding to the plurality of types of through holes, and thus are classified in size from the LED having a large diameter to the LED having a small diameter and are sequentially inserted into the through holes in a state of being included in a suspension 140.

FIGS. 8A to 8C describes one of the above-described methods as an example, and as shown in FIG. 8A, when each of B LEDs 110-1 for emitting blue light has the greatest diameter, first, the B LEDs 110-1 are located on the substrate 120 in a state of being included in the suspension 140, and then a pressure difference between an upper side and a lower side of the substrate 120 is generated to move the suspension 140 in a downward direction through the through holes of the substrate 120 so that the B LEDs 110-1 included in the suspension 140 are inserted into a first through hole 121-1 having the greatest inner diameter to be upright. The B LEDs 110-1 which are not inserted due to a shortage of the first through holes 121-1 among the B LEDs 110-1 included in the suspension 140 remain without being inserted into a second through hole 121-2 or third through hole 121-3 having a smaller diameter. The B LEDs 110-1 which remain without being inserted into the first through hole 121-1 are removed.

Further, as shown in FIG. 8B, each of R LEDs 110-2 for emitting red light with the second greatest diameter after the B LED 110-1 is inserted into the second through hole 121-2 corresponding to the R LED 110-2 to be upright in the same manner as above. Further, after removing the R LEDs 110-2 which remain without being inserted into the second through hole 121-2, finally, as shown in FIG. 8C, each of G LEDs 110-3 for emitting green light with the smallest diameter is inserted into the third through hole 121-3 to be upright.

Here, since adjacent three types of through holes 121-1, 121-2, and 121-3 having inner diameters of different sizes are formed as one group, the R LED 110-2, the G LED 110-3, and the B LED 110-1 form one group after alignment is completed. However, a relative size of each of the above-mentioned R LEDs 110-2, G LED 110-3, and B LED 110-1 is only an example, and may be differently formed.

When applying the above-mentioned method, micro LEDs having various sizes may be disposed in various shapes.

Third Modified Embodiment

FIG. 9 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a third modified embodiment of the present disclosure.

As shown in the drawings, in the third modified embodiment of the present disclosure, like the embodiment before modification, a substrate 120 has a thickness greater than a vertical width of each of micro LEDs 110 so that the micro LEDs 110 are entirely inserted into through holes 121 of the substrate 120. However, in comparison with the embodiment before modification, the through hole 121 of the substrate 120 is formed to have an inclined portion in which an inner diameter is not identically formed from an upper side to a lower side and gradually decreases from the upper side to the lower side. Further, the micro LED 110 has a diameter uniform from a lower end portion to an upper end portion.

According to the configurations of the third modified embodiment, as shown the drawing, there is an advantage in that the lower end portion of the micro LED 110 is fixed by crossing the inclined portion of the through hole 121 of the substrate 120 even when a separate stopper member is not provided.

Fourth Modified Embodiment

FIG. 10 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a fourth modified embodiment of the present disclosure.

As shown in the drawings, in the fourth modified embodiment of the present disclosure, like the embodiment before modification, a substrate 120 has a thickness greater than a vertical width of each of micro LEDs 110 so that the micro LEDs 110 may be entirely inserted into through holes 121 of the substrate 120. However, in comparison with the embodiment before modification, the through hole 121 of the substrate 120 is formed to have an inclined portion in which an inner diameter is not identically formed from an upper side to a lower side and gradually decreases from the upper side to the lower side, and in addition, the micro LED 110 has a diameter which gradually increases from a lower end portion to an upper end portion.

According to the configurations of the fourth modified embodiment, as shown the drawing, there is an advantage in that the upper end portion of the micro LED 110 is fixed by crossing the inclined portion of the through hole 121 of the substrate 120 even when a separate stopper member is not provided. In the case of the fourth modified embodiment, even in comparison with the third modified embodiment, since the upper end portion of the micro LED 110 instead of the lower end portion spans the inclined portion, it can be seen that more stable supporting and fixing may be performed. However, when the micro LED 110 is formed to have a diameter which is greater at the upper portion than at the lower portion, the micro LEDs 110 may be correctly stood and aligned by applying an additional force such as a dielectrophoretic force.

Fifth Modified Embodiment

FIG. 11 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a fifth modified embodiment of the present disclosure.

As shown in the drawing, in the fifth modified embodiment of the present disclosure, in comparison with the embodiment before modification, a micro LED 110 is provided in a shape having a diameter which gradually increases from a lower end portion to an upper end portion to be fixed by crossing an upper inlet of a through hole 121 of a substrate 120.

According to the configurations of the fifth modified embodiment, unlike the embodiment before modification, since the micro LEDs 110 are not completely inserted into the through holes 121 of the substrate 120, stability for maintaining a vertically aligned state may be partially reduced, but the micro LEDs 110 may be fixed by crossing the through holes 121 of the substrate 120 even when a separate stopper member is not provided. Further, in comparison with the embodiment before modification, since a second conductive layer 113 and an active layer 112 of the micro LED 110 is exposed at an upper side of the through hole 121, a more abundant quantity of light may be emitted at an upper side of the substrate 120. Accordingly, the fifth modified embodiment may be more appropriate for application to a light emitting device which requires an abundant light quantity in comparison with the former embodiments.

Sixth Modified Embodiment

FIG. 12 is a cross-sectional view of an LED assembly manufactured through an LED assembly manufacturing method according to a sixth modified embodiment of the present disclosure.

As shown in the drawings, in the sixth modified embodiment of the present disclosure, in comparison with the embodiment before modification, a substrate 120 has a thickness smaller than a vertical width of each of micro LEDs 110, so that at least one portion of an upper portion and a lower portion of the micro LED 110 partially protrudes from a through hole 121 of the substrate 120. In the case of FIG. 12, an example in which a first conductive layer 111 and a second conductive layer 113 of the micro LED 110 protrude from a lower side and an upper side of the substrate 120 is described, and as described above, when the micro LED 110 protrudes from the upper side and the lower side of the substrate 120 without being inserted into the through hole 121 of the substrate 120, there is an advantage in that an abundant quantity of light may be obtained at the upper side and the lower side of the substrate 120 in comparison with the former embodiments.

In the case of FIG. 12, although the example in which the micro LED 110 protrudes from both the upper side and the lower side of the substrate 120 is described, the micro LED 110 may be biased to protrude from only the upper side of the substrate 120 or only the lower side of the substrate 120. In this case, since a more abundant light quantity may be obtained only in a biased direction of the micro LED 110, the biased direction may be selected according to a light emitting device to which an LED assembly is applied.

However, when the micro LED 110 protrudes from the lower side of the substrate 120, a problem of how to stop and fix the micro LED 110 to prevent it from completely passing through and separating from the through hole 121 of the substrate 120 during a process of aligning the micro LEDs 110 using a flow of a suspension 140 is faced. In this case, the problem may be simply solved by not bringing the above-mentioned stopper plate 122 into contact with a lower surface of the substrate 120 through padding so that the stopper plate 122 and the substrate 120 may face each other with an interval therebetween, and the problem may also be solved by modifying shapes of the through hole 121 of the substrate 120 and the micro LED 110 as shown in the above-described first modified embodiment to fifth modified embodiment.

The above-described modified embodiments are modifications in a way of changing the thickness of the substrate 120 on the basis of the vertical width of the micro LED 110, and the shapes of the micro LED 110 and the through hole 121 from the embodiment before modification, and more various modifications are possible in the same manner or through partial changes and combinations of the above-described various embodiments.

In a vertical alignment method of a vertical type micro light emitting diode (LED) according to the present disclosure and an LED assembly manufacturing method using the same, a plurality of micro LEDs can be vertically and uniformly aligned and the aligned state can be stably maintained due to a unique concept of moving a suspension including the micro LEDs to through holes of a substrate.

Further, in the present disclosure, since directions of a first conductive layer and a second conductive layer are not mixed due to the vertical alignment of the micro LEDs, a first electrode and a second electrode corresponding to the first conductive layer and the second conductive layer are very simply formed, and since a light emitting direction is not dispersed and is concentrated in one direction, the improvement of light efficiency and an abundant light amount can be expected.

In addition, since the degree of integration of the micro LEDs per the same area is significantly improved in comparison with a horizontal alignment method, the present disclosure is advantageous for being applied to various light emitting devices, which require high quality images with an abundant light quantity, in addition to a high resolution display.

Although preferable embodiments of the present disclosure are described in the above, the present disclosure may use various changes, modifications, and equivalents. It is apparent that the embodiments may be appropriately modified to be identically applied in the present disclosure. Accordingly, the above-mentioned content does not limit the scope of the present disclosure determined by limit of the claims which will be described below. 

What is claimed is:
 1. A vertical alignment method of a micro light emitting diode (LED) which aligns a micro LED whose vertical width is greater than a lateral width, the vertical alignment method comprising: preparing a substrate provided with a plurality of through holes formed in a thickness direction; locating micro LEDs to be aligned on the substrate in a state of being included in a suspension which provides buoyancy; and generating a pressure difference between an upper side and a lower side of the substrate and moving the suspension in a downward direction through the through holes of the substrate to induce the micro LEDs included in the suspension to be aligned in an upright state by being at least partially inserted into the through holes, wherein a stopper plate having discharge holes is installed on a lower surface of the substrate to allow only the suspension to pass downward through the discharge holes and block the micro LEDs so that the micro LEDs remain in the through holes of the substrate.
 2. The vertical alignment method of claim 1, wherein the suspension including the micro LEDs is applied on an upper surface of the substrate and thus the micro LEDs are located on the substrate and one through hole of the substrate corresponds to one micro LED.
 3. The vertical alignment method of claim 1, wherein each of the micro LEDs is provided so that a lower portion has a high density in comparison with an upper portion, and thus the lower portions of the LEDs having a relatively high density are guided to move in a downward direction in the suspension moving downward when the micro LEDs are aligned.
 4. The vertical alignment method of claim 1, wherein the micro LED is formed to have a diameter which is uniform from a lower end portion to an upper end portion.
 5. The vertical alignment method of claim 1, wherein the micro LED is formed to have a diameter which gradually increases from an upper end portion to a lower end portion.
 6. The vertical alignment method of claim 1, wherein the micro LED is formed to have a diameter which gradually increases from a lower end portion to an upper end portion.
 7. The vertical alignment method of claim 6, wherein the micro LED is fixed by crossing an upper inlet of the through hole of the substrate.
 8. The vertical alignment method of claim 1, wherein the substrate is provided so that each of the through holes has the same inner diameter from an upper side to a lower side thereof.
 9. The vertical alignment method of claim 1, wherein the substrate is provided so that each of the through holes has an inclined portion in which an inner diameter is changed from an upper side to a lower side thereof.
 10. The vertical alignment method of claim 1, wherein the substrate is provided so that each of the through holes has an inclined portion in which an inner diameter gradually decreases from an upper side to a lower side thereof, and thus the micro LED is fixed by crossing at one point of the inclined portion in a state of being inserted into the through hole of the substrate.
 11. The vertical alignment method of claim 1, wherein: the substrate is provided with various types of through holes having inner diameters of different sizes; the micro LEDs are provided in various types having diameters of sizes corresponding to the various types of through holes; and the LEDs are classified from large to small in size to be sequentially inserted into the through holes.
 12. The vertical alignment method of claim 11, wherein: three types of through holes having inner diameters of different sizes form one group in the substrate; and an R LED for red light emission, a G LED for green light emission, and a B LED for blue light emission are inserted into the three types of through holes forming the one group.
 13. The vertical alignment method of claim 1, wherein: a first conductive layer, an active layer, a second conductive layer are sequentially located from a lower layer to an upper layer in the micro LED; one of the first conductive layer and the second conductive layer is an n-type nitride semiconductor layer; and the other of the first conductive layer and the second conductive layer is a p-type nitride semiconductor layer.
 14. The vertical alignment method of claim 1, wherein the micro LED has a vertical width of 100 nm to 10 μm.
 15. An LED assembly manufacturing method including a process of vertically aligning the micro LEDs on the basis of the substrate by the vertical alignment method of a micro LED of claim
 1. 16. An LED assembly manufactured through the LED assembly manufacturing method of claim
 15. 17. A micro LED light emitting device including the LED assembly of claim
 16. 